Control of electric motors and apparatus therefor.



P. N. )ONES L l. W. WELSH.

CUNIHUL UF ELECTRIC MOTORS ANUAPPARATUS THEREFOH.

APPLICAHGN r|LD1ULY|r.|s15

1 ,264,941 Patented May 7,1918.

4 SHEES-SHEU' 3.

P.N.1UNES L 1. W. WELSH.

CUNHwL 0F ELECmC Mamas AND APPARMUS IHEREFOH.

APPLICATIGN HLE )ULY II. \9l5.

Patented Muy T, i918.

4 SHEETS-SHEET 4.

INVENTORS Q WN. @www w wm, La CQMW QMN UNITED STATES PATENT OFFICE.

PEARL N. JONES, OF PITTSBURGH, AND JAMES W. WELSH, 0F OAKMONT, PENNSYL- VANIA.

CONTROL 0F ELECTRIC MOTORS AND APPARATUS THEREFOB.

Application led July 17, 1915.

T 0 all ulwm it may concern.'

Bc it known that wc. Pratici, N. Jesi-1s and Jam-:s W. 'Ensii, both citizens of the l'nited States. and residents of Pittsbnrgh and Oakinont. respectively, Alleglieny county, Pennsylvania, have invented a new and useful Improvement in Control ot Electric Motors and Apparatus Therefor, ot' which the following is a full, clear, and exact description. reference being had to the accompanying drawings` forming part of this specification, in which- Figure 1 is a diagrammatic view showing a plurality of motors, their circuit connections and circuit controlling switches, together with a development of one form of master controller for controlling such switches.

Fig. Q is a diagram showing graphically the seventeen different motor connections and relations in the seventeen di'erent positions of the master controller.

Fig, 3 is a view similar to Fig. 1, but showing a modification.

Fig. 4 is a view similar to Fig. 2, showin aniodiication.

Our invention has relation to the control of electric motors, and is especially applicable for use in connection with the motors of electrically piopelled vehicles.

The invention, considered as a whole, is particularly adapted to the control of a pluralitdl of electric motors having separately excited field windings. By separately excited as used herein and in the appended claims, we refer to field windings which are in shunt, or which are excited by circuit connections which are independent of the armature circuits, although the current for both the armature and field windings may be derived from the same source.

The invention may be used either with motors in which all the field windings are separately excited, or the field windings may be compound wound, their main windings being separately excited, with secondary win ings which are in series with the armature windings.

One object of our invention is,

but

to provide a novel method of and means for accelerating a 'plurality of electric motors by a series of gradual and easy transitions, and with the use of a minimum amount of ex- Specitlcaton of Letters Patent.

Patented May 7, 191s.

Serial No. 40,441.

tcrnal resistance, particularly in the armature circuits, the motors being shifted from series to series-parallel relation, and thence to full-parallel relation, mainly by changes in the field strength of the motors.

A further object of the invention is to provide an efiicient and economical method ot' and apparatus for the cont-rol offa plurality of motors whereby the motors may he operated rcgeneratively. That is to say, in which, in coasting down a grade, or in bringing the car to a stop, the motors may be made to act as generators and to return hc generated current back into the supply Our invention will be best understood by reference to the accompanying drawings in which several modifications are illustrated, and which will now be described. itheilig premised, however, that the method of control, particularly as to its minor steps, may be considerablyT varied, and that other forms of apparatus having the general principles and features of operation of those herein described may lie used, without departing frointhe spirit and sco )e otthe invention as defined in the appended claims.

Referring first to that forni of our invention illustrated in Figs. l and 2, #1, #2, #3 and #i designate respectively the armatures of four electric motors. For the 'purposes of this invention we, prefer to cniplo)1 the type of motors known as interpole motors in which the effect of crossmagnetization is reduced 'to a minimum. F61, F82, Fc and Fe* designate, respectively. the separately excited field windings of these motors, and which windings we prefer to keen permanently connected in series with eac other. Ar designates external resist.- anco which can bc connected in thi` armature circuit. Fr designates sectional external resistance connected in series with the scparately excited eld windings. T designates the connection with the supply side of the circuit. Gr, wherever seen. designates a return or ground connection. A and B areV switch vdevices for connecting the armature.V

J and K are switch devices for grounding' vso the armature windings of motors #1, #2 and .#3, motor #4 being shown as having a permanent ground connection. P, Q, R, S and U are switch devices whereby the field windings or portions thereof may be short-eircuited.

MC designates a master controller, shown in the usual developed form, and which is for controlling the actuators of the various switches just referred to. The contact fingers a, b, c, etc., shown in Fig. 1 are connected, respectively, with the actuators of the various switches A, B, C, etc., finger d being connected to the actuator of switch A, finger to the actuator of switch B, and finger c to the actuator of switch C, etc. To simplify the drawings, these connections, together with the actuators, have been omitted, since we may use any suitable actuators known in the art, such, for instance, as those shown in our Patent No. 1,109,338, dated September 1, 1914. It will be readily understood by those familiar with the art, that when one of the fingers ft, c, etc., is in engagemeut with the contact shown opposite to such finger on the drum MC, the corresponding actuator will be energized and its switch closed, while at all other 4times that particular switch will be open. The several positions or notches of Athe controller are indicated by the broken vertical lines 1 to 17'of Fig. 1; and the circuit conditions corresponding to these several positions are shown in the series of 4diagrams of Fig. 2, these diagrams being numbered to agree with the numbering of the positions. or notches indicated in Fig. 1.

RS designates a field reversin switch of any well known type. CS deslgnates the usual platform switch or circuit breaker.

In accelerating the motors, when the master controller is moved to its first position, switches A, C, D, E, L, M, N and 0 are closed, thereby connecting the armatures of the four motors in series with each other and with the resistance Ar, the field windings of. the four motors being also connected in series with each other, but in parallel with the armatures, and the resistance F r is short-circuited by means of the switches L, M, N and O.

At the second position, the only change is to energize the switch B, thereby shortcircuiting the resistance Ar.

At position 3, switches L and M are opened successively, thereby throwing a portion of the resistance Fr into series with the field windings and to this extent weakening the strength of the fields collectively.

On -the forth position, switches P, Q, and R are energized (the switches otherwise remaining as in position No. 3). The closing of switches P, Q and R short-circuits the field windings of motors #1 and #2, this being done in three steps in passing from of the field of motor #1, and 'finally by position 3 to position 4. The first step consists in short-circuiting the field of motor #2, followed by the short-circuitmg of' half the remaining half of motor #1.

At the fifth position, switch G is closed and switch D opened. The effect of' this is first to short-circuit and then to opencircuit the armatures of :#:1 and #2 motors and to connect. the armatures of #f3 and #4 motors in series across the line.

In the sixth position, the field of #l and #2 motors are again restablished by two steps. The first. step consists in opening the short-circuit on field Fe by the opening ofY the switch R, and substantially simultaneously therewith short-circuiting a portion of the resistance F7- b switch L. field Fe1 is then opened by the opening of switch Q. More of the resistance Fr is uien short-cimmed by am closing gf the switch M.

theelosing of the *l The shortc1rcuit on one half of In' passing to the seventh position, the

Fr beingshort-circuited.- The connection of the #l and #2 armatures across the line is 'effected by the closin of the switch J; switches P, Q, R, S and. areopemand switches L, M,'N and O are closed. The

short-circuits of ali the field windings are l thus opened, and all the resistance Fr is shortlcircuited. l

At the eighth position a portion of the external field resistance Fr is cut in in two steps by the successive opening of the switches L and M.

At the ninth position the remainder of the field resistance has been cut in by the successive opening of the switches N and O.

At the tenth position the fields of #l and .#:3 armatures are short-circuited, this condition being reached by first shortcir cuiting half the fields of #1 and #3 and at the same time short-circuiting a portion ofthe external field resistance, and next by sliort-circuiting the remaining halves of Fcl and Fe". and at the same time short-circuiting additional portions of the external field resistance. The two-step short-circuiting of the fields is effected by the4 closing of yswitches P and Q, S and U. The shortswitches F and H and the opening of switches C and E.

At the twelfth position the fields Fel and FeB are restablished. This is eifected by first opening the short-circuit on onehalf of each of these'fields by opening the switches P and S. At the same time a or tion of the resistance F'r' is short-circulted by closing the switch N. The short-circuit on the remaining half of F61 and Fea is then o cned by opening the switches Q and U, an short-crcuiting the remaining portion of the resistance Fr by closing the switch O. Y

At the thirteenth position the closing of switches I and K connects the #land #3 armatures directly across the line in parallel with each other and in v arallel with the armatures #2 and #4. A `four armatures are now in parallel and all of the external resistance Fr is short-circuited.

At the fourteenth position a portion of the resistance F1' is cut into circuit by the opening of the switch L; and on the fifteenth, sixteenth and seventeenth notches, additional portions of this resistance are put in circuit by the successive o ening of the .switches M, -N and O, unt at the seventeenth position, all the external resistance is It will be noted that after the armature resistance Ab' has been short-circuited by the closing of switch B in passing from the first to the second position, 1t remains shorteircuited throughout all the successive positions; and that the chan es in asslng from series to series-par el an from series-parallel to full-parallel, are effected wholly by variation in the strength of the individual fields and by changes 1n the external field resistance.

It will be noted that the rst step preparatory to passing from series to seriesparallel is to increase the of all the motors by cutting into circuit a portion of the resistance Fr and thereby weakening the fields of the motors. The field windin s of #1 and #2 are then short-circuito vthrowing a higher voltage upon #3 and #-4. Armatures #1' and #2 are then connected in series-parallel with armatures #3 and #4 with their Aindividual fields reestablished and the fields of all the. motors strengthened by the `removal .of the externa resistance.

In passing from series-parallel to parallel, substantially the same changes take,

place. The motors are first accelerated while -in series-parallel relation by cutting in external resistance fto weaken their fields. The fields of two of the motors are next partially and then wholly short-circuited, while the two remaining fields are strengthened both by the short-circniting of some external resistance, as well as by the shortcircuiting of the other two fields. Of

course, the short-circui-ting of some ofthe all four motors being strong. The fieldsare then weakened collectively by cutting in successive portions of the external resstance, and thus further accelerated.

It will be readily seen that the provision of the separately excited fields and the connections of the motors `at the different positions readily permits of regenerative operation at any position of the controller. Whenever the speed of the car exceeds the speed corresponding to thenormal motor speed at that position of the controller, the counter-electromotive force develo ed by the motors will be higher than voltage, and current will be fed'hack into thel line. For example, this will occur when the car is runnin at the speed corresponding to the wea ened se arately excited fields, and these fields vare t en strengthened by cutting out the external resistance. Y The increase in field strength inthis way makes the -counter-elec-.trom'otive forcey of the motors higher than the line voltage and resuits in regenerative operation. TheA saine eline result is accomplished when the four l motors operating at the s eed and field.

strength corresponding to t e full-parallel position with the stro est field are cut back into the series-paralle position in which two motors are in series across the line, thereby permitting the sum of the counterelectromotive forces of these two motors 1 to feed current back into the line against the line voltage. This process is, however, eii'ected gradually, as will be noted, since in changin from the full-parallel to the series-parel el position, Vthe fields are first gradually strengthened collectively; thefields of two of the motors are short-cir#4 cuited in two steps, and the external field resistance, is cut back into the circuit to maintain a constant field current in the remanin motors. Then when the field is reestablis ed on the first two motors, the ex ternal field resistance is again cut* in, so. that `when the series-parallel poe'ritionY is reached, the motors are operating' Ywitltffa "further `weakened field.

The motorman may, therefore, by gradually notching back the controller lin descending a grade, or in bringing the car to a stop, constantly maintain the car at a greater speed t an the normal speed value of the. controller position at any given time; and thus. give a practically continuons regeneratio iis Fig. 3 shows a modification of our invention 1n which the only chan e, as com ared withthe form first describe consists in the use of an auxiliary field winding Fex in series with each of the armatures and each of these windings being preferably main tained permanently in series with its armature. The same reference characters have been applied to Fig. 3 as to Fig. 2, with a prime mark added thereto. Substantially the only difference in the apparatus shown in Fig. 3 over that shown in Fig. 1 is that instead of employing the switches L, M, N, O, P, Q, R, S, U, and actuators therefor controlled by contacts on the master controller, the field coils and the resistance F r are provided with the leads Z', m', n', o', p', Q', s', t', u', 'u' and fw', which are directly connected respectively to the similarly lettered contact lingers of the master controller MC. This requires the provision ofthe additional contact fingers t, 'u and w', with the additional corresponding contacts indicated on the controller drum. Insulation X is 'also preferably provided on the drum at the points indicated in Fi 3.

The purpose of the auxi iary series windings Fex is to give the motors a droopin speed character, and has the advantage o improving the equalization of the load between motors having driving wheels of dif-l ferent diameters, or having inequalities in their field magnet circuits. These auxiliary series windings will also prevent any one motor from taking an excessive load when its separately excited field is weakened, since the increased current which is drawn from the line in this case will strengthen the field magnetization. This is of value when the load is exceptionally heavy or when'heavy grades are encountered.

These auxiliary windings also form a further means of graduating the amount of regenerated current when operating the mo` tors regeneratively. In this case the series windings oppose the magnetization produced by the separately excited windings and thereby act to reduce the counter-electromotive force when the regenerated current fed back into the line becomes excessive. In other words, the motors in this case act as differentially compound wound (generators. For this reason they do not nee an equalizer connection, or direct connection between their armature brushes. l For exam le, if one motor does not regenerate as s. resu t of poor magnetic circuit or of slower speed resulting from a different wheel diameter; and if the other motors actin as generators should feed into this motor, t e eii'ect would be to increase its field strength and thereby increase its counter-electromotive force and cause it to regenerate. On the other hand, a motor which tends to regenerate too much current will thereby automatically weaken 4connections are the same as in its field and thus bring it back to the proper condition.

In Fig. 4 we have illustrated a modified system of control in which the separately excited fields, instead of being permanently connected in series across the line, are connected in parallel across the line.' In this drawing, corresponding parte are given the same reference characters as in Fig. 2, with the numeral 3 applied thereto. The auxiliary field windings also used in this system, as in that shown in Fig. 3, are marked Fey, and the main shunt field windings are marked Fez, Fea, Fea, Fez.

It will be seen that in the first position the armatures with their auxiliary series windings areV in strai ht series and with their fields all in para el, the amature resistance being in circuit, but the field resistance, which is in series with the parallel main field windings, being short-circuited. In position 2 the armature resistance is shortcircuited. In position 3 the short-circuit for the field resistance is removed. In position 4 the separately excited field windings of two of the motors are open-circuited. In position 5 the two armatures whose fields are thus open-circuited are cut out. In position 6 the two open-circuited fields are re-connected in a manner to reverse the direction of flow of the current therethrough preparatory to reconnecting the armatures of these motors as shown at position 7-. At such po sition, it will be seen that the armatures are reconnected with the current fiow .therethrough reversed, and this makes it necessary to reverse the fiow through the corresponding fields. In the eighth position, the the seventh, except that a portion of the field resistance is put, into circuit. In position 9 the entire field resistance is cut into circuit. At the tenth position, the field resistance is short circuited and the fields of-armatures #l and #4 are open-circuited. At the eleventh position, armatures #l and" 4 are o en cireuited. At the twelfth posit1on, the elds of these two armatures are reconnected to cause reverse current f'low therethrough; and at the thirteenth position the four armatures are connected in parallel across the line with the field resistance short-circuited. At the fourteenth position, a ortion of this short.

circuit is removed, an entirely removed.

By the term weakening as used herein and in the claims I intend to cover either the elimination o either a portion or the entire field windin ofthe motor or motors affected; and it w1 be seen that this may be accomplished either by shortfcircuitmg or open-clrcuiting. 4

In those claims in which we have referred to closing the motor armatures in certain relations, we intend to include also the auxilat position 15-it is' soA soepel i 53 iary series winding, which is permanently in series with the armatures in the-forms where these auxiliary windings are used.

We claim:

1. In the control of electric motors having separately excited field windings, the method of acceleration .which consists in first connecting the motor armatures in series across the line, then increasing their speed by'weakenin their field stren ftli collectively, and algso by further weaeninfr the field stren h of some of the motors individually, an then reconnecting the motor armatures into smaller groups across the line, while running them at the increased speed due to such weakening, and increasing their field strength substantially simultaneously with their reconnection, substantially as described.

o 2. The method of accelerating a plurality of electric motors having separately excited field windings, which comprises connecting their armatures in series across the line, then weakening the fields of all of the ino- :5 tors collectively, and then further weakening the field strength of some of them to increase the voltage on the others, and then reconnecting such armatures across the line inseries-parallel with the remaining arma- 50 tures, and increasing their field strength substantially simultaneously with their re` connection, substantially as described.

3. The method of accelerating a plurality of motors having separately excited field windings, which comprises connecting their armatures in series across the line, then weakening the fields of all of the motors collectively and also of some of them individually to increase the voltage on the others, then reconnecting such armatures across the line in series-parallel with the remaining armatures and substantially simultaneously therewith increasing their field strength, and then again weaenin the fields of some of the motors, and ally connecting all the motors across the line in parallel, substantially as described. 4. In the control of a pluralit of electric i motors, having separately exci field windings, the method which consists in first connecting the motor armatures in series across the line, then weakening the fields of one group of motors and reconnecting them in series-parallel with another group, then weakening the fields of the motors in both groups, and then successively connecting ifferent armatures in parallel across the line, substantially as described.

' 5. In the control of a plurality of electric motors having separately excited field windings, the method which consists in weakening the fields of one group of motors and then reconnecting their armatures in series-parallel with another group, then weakening the fields of the motors n both groups, then successively connectin different armatures iu parallel across the me, and strengthening the fields of the reconnected armatures both when reconnecting them in series-parallel and `when reconnecting them in full-parallel, substantially as described.

6. In the control of a plurality of elec- 'ti'ic motors having separately excited field windings, the method which consists in first connecting llic motor armatures in Series across the line, then weakening the fields ot' all the motors collectively, and further weakenin r the fields of some of the motors individua ly, and then rcconneetinr the motor armatures having the lndividufilly cned fields in series-parallel with the other armatures which have strenffthened indivicl'nal fields, substantially as tdescribed.

7. In the control of a plurality of electric motors having separately excited field windings, the method which consists` in first connecting the motor armatures in series across the line, then weakening the fields of all the motors collectively, and further wealreni-n individua ly, and then reconnecting the armatures having the individually weakened fields in series-parallel with the other armatures, with strengthened individual fields, and then weakening the field strength of' the motors as a whole, substantially as described.

8. In the control of a plurality of electric motors having separately excited field windings, the method which consists in first connecting the motor armatures in series across the line, then weakening the fields of all the motors and also further weakening the individual fields of one group of motors, and reconnecting such armatures with restablislied fields in series-parallel with another group, and then subsequently again weakening the fields of some of the motors and connecting all the motors across the line in parallel, substantially as described.

9. The method of regeneratively operating a plurality of electric motors having separatively excited fields, which consists in increasing the field strength of some of the motors and then changing their connection from parallel to series-parallel, and decreasing their field strength in reconnecting them, and after reconnection, again increasing their field strength, substantially as described.

10. The method of regeneratively operating a plurality of electric motors having separately excited fields, which consists in increasing the field strength of some of the motors and then changing their connection from arallel to series-parallel, and substanti ly simultaneously therewith decreasing their field strength, and subsequently connecting all the motors in series across the weak- 8o A the fields of some of the motors 9o 4 line und increasing their field strength, substantially as described.

1l. The method of regenerati'vely operating a plurality of electric railway motors, having separately excited main field windings, and auxiliary windings in series with their armatures, which consists in increasin the field strength of some of the motors an then changin their connection from parallel to series-pare lel, and decreasing their iield strength in reconnecting them, and after reconnection, again increasing their field strength. substantially as described.

12. In the control of a plurality of elec-r tric motors having separately excited fields, the method of changing the motor armatures from series-parallel to parallel relations, which consists in weakening the fields of all of themotors collectively, and further weakening the fields of one group of motors, and connectin the armatures of another group across t ie line in parallel, and then connectino the armaturesof the first group in parallel across the line and with reestablished fields, substantially as described.

13. The combination of a plurality of y electric motors having separately excited field windings and having external resistance in series with all of said windings, of switch devices and connections arranged to connect the motors in series, in series parallel and in full parallel, and also havin means for ailecting the field strength of a of the motors collectively by varying the amount of suoli external resistance in circuit there with, and for further chanin the field strength of the motorslindivi ua y b short eircuiting the field windings thereo substantially as described.`

14. The combination of a plurality of electric motors having se arately excited field windings, of switch evices and connections arranged to connect the motors in series-parallel, and i'n full-parallel, together with means for v in the field strength of the motors indivi ua y, and other means for varyin' their field strength collectively, substantially as described.

15. The combination with a plurality of electric motors having separately excited Lecce-li electric motors having separately excited main iield windings, and auxiliary field windings permanently in series with their armatures, of switch devices and connections arranged to connect the motor armatures und their windings in series, in series-parallel und in full-parallel, together with means ior changing the eld stren h ofthe main vfield windings both indivi ually and collectivelv, substantially as described.

17, rllhe combination with a plurality of motors having separately excited field windings permanently connected in series, of means for operating the motors regeneratively for re ucing their speed, said means comprising switch devices and circuit con* nections constructed and arranged to change the motor armatures from parallel to seriesparallel and then to series, together with means for varying the field strength of at least some of the motors in reconnecting them in their new relations, substantially as described. 4

18. The combination with a plurality of electric motors, and with external resistance for connection in series with the field windings of all of said motors, of switch means arranged to connect the external resistance, or portions thereof, in series 4with the eld windings of all of the motors,- and substantially simultaneousl therewith to shortcircuit some of the fiel windings, substantially as described.

In testimony whereof, We have hereunto set our hands.

PEARL N. JONES.

Witnesses:

Gao. K.MCGUNNEGLE, T. W. ERNST.

JAMES W. WELSH. 

